Hot gas engine power control device

ABSTRACT

A Stirling type hot gas engine controls power by means of a dead volume chamber coupled to the low temperature working space of each cylinder wherein a movable wall in each chamber is connected for changing the volume. Means is provided for using gas pressures for movement of the walls. One way valves are provided for control of pressures within the dead volume chambers.

States Patent Gothberg Nov. 19, 1974 HOT GAS ENGINE POWER CONTROL DEVICE Inventor: Yngve Roland Gothberg, Malmo,

Sweden Kommanditbolaget United Stirling (Sweden) AB & Co., Malmo, Sweden Filed: Aug. 22, 1973 Appl. No.: 390,518

Assignee:

Foreign Application Priority Data Sept. 26, 1972 Sweden 44384/72 US. Cl. 60/525, 60/517 Int. Cl F02g 1/04, F02g i/06 Field of Search 60/5l7, 521, 522, 525

References Cited UNITED STATES PATENTS Rinia et al. 60/522 3,036,427 5/1962 Meijer 60/521 Primary Examiner-Edgar W. Geoghegan Assistant ExaminerAllen M. Ostrager Attorney, Agent, or Firm-Laurence R. Brown [57] ABSTRACT A Stirling type hot gas engine controls power by means of a dead volume chamber coupled to the low temperature working space of each cylinder wherein a movable wall in each chamber is connected for changing the volume. Means is provided for using gas pressures for movement of the walls. One way valves are provided for control of pressures within the dead volume chambers.

6 Claims, 5 Drawing Figures HOT GAS ENGINE POWER CONTROL DEVICE This invention relates to a multi-cylinder hot gas en gine power control device, the engine being of the type in which charges of working gas are kept separate from each other and for each charge there is a respective low temperature working chamber, and the device being of the kind (herein called the kind defined) comprising for each charge of working gas a dead volume chamber adapted to be connected to the low temperature working chamber of each charge.

One object of the present invention is to provide a power control device of the kind defined which is simple in manufacture, easy to handle and which allows a wide continuous variation of power output without having an external servo-mechanism.

A device of the kind defined according to the invention is characterised in that each of said dead volume chambers is partly limited by a movable wall and the movable walls are rigidly coupled together.

The scope of the monopoly sought is defined in the claims hereinafter, and how the invention may be put into practice is described in more detail with reference to the accompanying drawings, in which FIG. 1 schematically shows a hot gas engine provided with a power control device according to the invention,

FIG. 2 shows a servo-valve detail of the device of FIG. 1, and

FIGS. 3, 4 and 5 show other details of the device of FIG. 1.

Referring first to FIG. 1, the hot gas engine comprises four similar cylinders l 4. Consequently, to render the explanations below more simple and thus easier to understand, only details relating to one of the cylinders cylinder No. l will generally be described in detail.

The cylinder No. l accommodates a reciprocating piston 5 dividing the interior of the cylinder into an upper working chamber 6 and a lower working chamber 12 containing working gas. The upper working chamber 6 is connected via a system of heater pipes 7 to a re-generator 8 and a cooler 9. The cooler 9 is connected to the lower working chamber 10 of cylinder No. 2 via a cold gas connecting duct 11.

The lower working chamber 12 of cylinder No. l is connected to a cooler 13 and a regenerator 14 via a cold gas connecting duct 15. The piston 5 is provided with a piston rod connected to a conventional drive mechanism, not shown on the drawing.

The pistons of the four cylinders are displaced 90 degrees relative each other in their cyclic movements and each piston keeps two of the gas charges separate from each other. The upper working chamber of cylinder No. 4 is connected (via a conduit not completely shown) to the lower chamber 12 of cylinder No. 1 via the regenerator 14 the cooler 13 and the cold gas connecting duct 15.

The engine so far described is a conventional type of four-cylinder double-acting hot gas engine having four separate gas charges working according to the Stirling principle.

The cold gas connecting duct 15 is connected to a respective dead volume chamber 16 which is limited by a cylindrical wall 17 and a stationary wall 18 as well as a movable disc-shaped wall 19. Likewise each of the other cold gas connecting ducts is connected to its respective dead volume chamber. The movable wall 19 is rigidly mounted on a piston rod 20. The piston rod 20 is passed through the stationary wall 18 as well as through the other corresponding stationary walls limiting dead volume chambers connected to cold gas connecting ducts. The piston rod 20 also carries the other movable walls limiting dead volume chambers.

The dead volume chamber 16 and the other three corresponding dead volume chambers are connected to a conduit 21 via check valves, see for example the valve 22, allowing flow of gas only in the direction into said conduit 21. Thus the pressure in the conduit will correspond to the maximum value of the cyclic pressure of the working gas.

The conduit 21 terminates in a valve opening which, at the moment depicted in FIG. 1, is closed by a movable cylindrical valve member 23 arranged in a bore 24 of a housing 25 protruding at the right-hand end of the engine.

Each dead volume chamber limited partly by the right-hand side of each movable wall and partly by the left-hand side of a stationary disc-shaped wall e.g., the chamber 26 is directly connected to a conduit 27 terminating at the lower end of the bore 24 and via a branched conduit 28 also to the upper end of the bore 24. The housing 25 also contains a chamber divided in two parts by a flexible membrane 29, namely an upper chamber part 30 and a lower chamber part 31. The upper chamber part 30 is connected via a conduit 32 to a chamber 33 limited by the right-hand side of a movable wall and by the left-hand side of a stationary disc-shaped wall. The lower chamber part 31 is connected to the nearest dead volume chamber 34 via a conduit 35 containing a flow-restrictor 36.

The piston rod 20 is provided with an axial bore 37 which at its right-hand end telescopically engages a stationary pipe 38, the interior of which terminates at a side opening 39 of the bore 24, the termination being covered by the valve member 23 in the position shown.

The bore 37 communicates with each of the dead volume chambers via a conduit, for example the conduit 40, containing a non-return valve 41. Thus the pressure in the bore 37 will correspond to the minimum value of the cycling pressure of the working gas.

The left-hand end of the bore 37 is engaged telescopically by a slide 42 shown more clearly in FIG. 2 pivotally connected at 43 to a lever arm 44 pivotally connected to the rest of the engine and sealed at 45. Axial movements of the slide 42 relative to the rod 20 are limited by a pin 46 rigidly mounted in the rod and protruding into a slot 47 in the slide 42. The slide 42 is provided with an axial bore 48 communicating with the bore 37 of the rod 20. The bore 48 communicates with a circumferential groove 49 on the slide 42, the said groove 49 being covered by the surface 50 of a bore in a piston 51 carried by the rod 20 at the lefthand end thereof. The said piston 51 separates two chambers 52 and 53 as shown in FIG. 1.

The surface 50 is located axially between adjacent surfaces 54 and S5 of greater diameters. The surface 54 tenninates at the left-hand end surface of the piston 51, I

and a bore 56 provides a communication between the chamber 53 and the annular chamber limited by the slide 42 and the surface 55.

The chambers 52 and 53 communicate each with the cold gas connecting duct 15 via a conduit containing a respective flow restrictor 57 or 58. Thus the gas pressure prevailing in said chambers will normally correspond to the mean value of the pressure of the working gas.

The device as so far described will operate as follows:

If the slide 42 is moved towards the right by the lever arm 44 the bore 48 will establish a communication between the bore 37 and the chamber 53. The gas pressure in the chamber 53 will thus be lowered and the piston 51 will become moved towards the right, the said movement causing a closing of the connection to the bore 48. A movement towards the right of the piston 51 will cause a corresponding movement of the four movable walls limiting the dead volume chambers. Thus the size of each dead volume chamber will increase and cause a decrease of engine power output. Conversely, an increase in engine output will be obtained by moving the slide 42 towards the left.

A movement of the rod 20 towards the right will cause an increase of the pressure prevailing in the chamber 33 and a decrease of the pressure in the chamber 34. Thus the difference between the pressures in the chamber parts 30 and 31 will cause the membrane to move downwards and the valve member 23 will connect the conduit 28 and the interior of the pipe 38 via the opening 39. Thus gas will flow from the conduit 27 (and all chambers connected thereto) to the interior of the rod 20. Such flow of gas will accelerate the movement of the rod 20 (and the walls connected thereto) towards the right.

Conversely, if the rod 20 is moved towards the left the difference in pressure across the membrane 29 will cause a connection between the pipe 21 (containing gas of maximum cyclic pressure) and the pipe 27. This will accelerate the movement of the rod 20 towards the left.

As illustrated in FIG. 3 the piston 19 (as well as the other corresponding pistons) is provided with a protruding part 60 blocking the direct connection between the cold gas connecting duct and the dead volume chamber 16 when said dead volume chamber 16 has reached its minimum size. However, a bore 61 containing a non-return valve 62 (FIG. 1) is provided in the piston 19 to allow flow of gas in the direction from the dead volume chamber 16 into the working cycle. As soon as the pressure in the dead volume chambers has been reduced the membrane 29 will be moved downwards and the valve member 23 will open a passage between the conduit 27 (connected to all dead volume chambers) and the bore 37 (in which minimum cyclic pressure is maintained). Thus the gas pressure at both sides of each of the movable walls will become equalized. The engine output will now be raised not only because the dead volumes are as small as possible, but also because the mean pressure of the gas in the working cycle has been raised.

As shown in FIGS. 3 and 4 each of the stationary walls is provided with a movable valve member 63 which is normally retained by a spring 64 in the position shown in FIG. 3. However, if the movable piston 19 is moved towards its right-hand end position the I valve 63 will be moved towards the right into a position in which it will restrict the passage between the dead volume chamber and the cold gas connecting duct. Such restriction will have a braking effect upon the engine.

FIG. 5 shows a vertical section through the lever 44 perpendicular to the slide 42. The part of the lever 44 below the pivot 45 is located in a chamber 65 in which minimum cyclic pressure prevails. This pressure is the same as that prevailing inside the rod 20 and thus the force required to move the slide 42 will be very small.

What we claim is:

l. A multiple-cylinder hot gas engine power control device comprising in combination, a plurality of pistons each having a low temperature working chamber for receiving gas, a dead volume chamber coupled to each said working chamber, a movable wall in each of said chambers for changing the chamber volume, and means coupling said movable walls together for common movement to control the engine power.

2. A power control device according to claim 1, characterised in that said dead volume chambers are coaxially-disposed cylinders of equal dimensions and that said movable walls are pistons mounted on a common piston rod.

3. A power control device according to claim 1, characterised by a servo-mechanism for moving the movable walls, the said servo-mechanism comprising a piston mounted on a piston rod and dividing a cylinder into two compartments normally containing working gas at mean working cycle pressure, means being provided for lowering at will the pressure in one of the said compartments to minimum working cycle pressure.

4. A power control device according to any of claim 1 characterised by a flow-restrictor arranged between each low temperature working chamber and an adjacent dead volume chamber, the said restrictor being activated only when maximum travel of said movable walls is effected in the direction towards maximum dead volume.

5. A power control device according to claim 1 characterised by a valve activated by said movable wall closing the connection between the dead volume chamber and the low temperature working chamberwhen the movable wall is moved towards the end position causing minimum dead volume, said valve containing a passage having a non-return valve allowing gas to pass in the direction only from the dead volume into the working chamber.

6. A power control device according to claim 1 and in which each movable wall separates a dead volume chamber from another gas-containing chamber, characterised by a valve activated by the difference in mean pressures of the gas in these two chambers and governing connections between these chambers and sources for gas of minimum and maximum working cycle pressure in order to equalize said mean pressures. =l= =l= 

1. A multiple-cylinder hot gas engine power control device comprising in combination, a plurality of pistons each having a low temperature working chamber for receiving gas, a dead volume chamber coupled to each said working chamber, a movable wall in each of said chambers for changing the chamber volume, and means coupling said movable walls together for common movement to control the engine power.
 2. A power control device according to claim 1, characterised in that said dead volume chambers are coaxially-disposed cylinders of equal dimensions and that said movable walls are pistons mounted on a common piston rod.
 3. A power control device according to claim 1, characterised by a servo-mechanism for moving the movable walls, the said servo-mechanism comprising a piston mounted on a piston rod and dividing a cylinder into two compartmenTs normally containing working gas at mean working cycle pressure, means being provided for lowering at will the pressure in one of the said compartments to minimum working cycle pressure.
 4. A power control device according to any of claim 1 characterised by a flow-restrictor arranged between each low temperature working chamber and an adjacent dead volume chamber, the said restrictor being activated only when maximum travel of said movable walls is effected in the direction towards maximum dead volume.
 5. A power control device according to claim 1 characterised by a valve activated by said movable wall closing the connection between the dead volume chamber and the low temperature working chamber when the movable wall is moved towards the end position causing minimum dead volume, said valve containing a passage having a non-return valve allowing gas to pass in the direction only from the dead volume into the working chamber.
 6. A power control device according to claim 1 and in which each movable wall separates a dead volume chamber from another gas-containing chamber, characterised by a valve activated by the difference in mean pressures of the gas in these two chambers and governing connections between these chambers and sources for gas of minimum and maximum working cycle pressure in order to equalize said mean pressures. 